Hydrostatic driving mechanisms



F. KLOPP HYDROSTATIC DRIVING MECHANISMS May 29, 1962 Filed March 26, 1956 I5 Sheets-Sheet 1 u & ii 1 \S H R l1 3 l I 5 2 I I L 1 *2; &

1 2 A L i E E i I ll INVENT'OE Aka M /a May 29, 1962 F. KLOPP 3,036,528

HYDROSTATIC DRIVING MECHANISMS Filed March 26, 1956 3 Sheets-Sheet 2 f 44% M M May 29, 1962 F. KLOPP 3,036,528

HYDROS'I'ATIC DRIVING MECHANISMS Filed March 26, 1956 3 Sheets-Sheet 3 United States Patent 3,036,523 HYDROSTATKC DRIVING MECHANISMS Friedrich Klopp, Ohenitterstrasse 25, Solingen-Wald, Germany Filed Mar. 26, 1956, Ser. No. 573,826 Claims priority, application Germany Mar. 29, 1955 4 Claims. (61. 103-161) The invention relates to a hydrostatic driving mechanism and can be constructed as a pump or as a motor or as a combination of a pump and a motor.

Such hydrostatic driving mechanisms are already known, in which a plurality of pistons in the form of a stanshaped group are arranged to be radially movable in a cylinder housing which rotates about a central control plug containing suction and pressure channels; the pistons are urged outwardly by centrifugal force with their heads against a circular regulating ring, the axis of which is eccentric and adjustable with respect to those of the cylindrical housing and the control plug.

The invention is concerned with the problem of improving such driving mechanisms and in particular relates to improving their running and vibration characteristics.

According to the invention, an even number of piston groups are axially arranged together Will the least possible spacing so that each two piston groups are displaced by 180 one to the other, whereas the cylinder housings of the groups are secured against relative rotation and are radially movably connected together in the direction of their displacement. In this way, the rotary field of th motor or pump respectively lies over the whole circumference as regards such two associated groups.

At the same time, the unbalance of the two associated groups, which is caused by the eccentric rotation of the pistons, is statically compensated. Should at least four of such groups be provided, a dynamic compensation is also given. The feature that the cylinder housings of the groups are secured against relative rotation and are radially movably connected together in the direction of their displacement ensures that no tilting movement of the cylinder housings on the control plug with a greater number of associated cylinder housings will result.

Silent running and freedom from vibration of the driving mechanism are further improved in the region of the running surface of the control plug between the suction space and the pressure space which is in communication with a source of a substantially constant pre-pressure which subjects the cylinder to a low fluid pressure before completion of the suction stroke preventing a return pulse occurring in the cylinder caused by the large pressure within the pressure space acting on the entrained air in the oil. It is to be noted that any pump operates with a volumetric efllciency, which is merely another expression for the phenomenon that the whole of the existing cyinder space is not completely filled during the suction stroke. In other words, the oil drawn by the pump from the reservoir is mixed with entrained air. A mixture of a liquid with air is a physical phenomenon and the degree of mixing with air is dependent upon several factors, such as temperature, viscosity of the liquid and pressure. Normally as the revolving cyinder and piston move from the suction side to the pressure side, the oil within the pressure side enters the incompletely filled cylinder spaces spasmodically causes a pulsing vibration. This has the result that the oil column within the cylinder undergoes oscillation. If vibrations of the machine driven by this pump occur in the same frequency range, the Whole machine vibrates. This oscillation is prevented in the device of the invention by subjecting the cylinder to a small prepressure before the cylinder communicates with the pressure or discharge section of the pump.

3,935,528 Patented May 29, 1962 Due to the above-described features of the invention no interruption in the constancy of the pressure dissemination on the pressure side and in changing over from the suction side to the pressure side occurs. It may thus be established that the entrained air in the oil at a pressure of 15-30 ats. is completely absorbed, so that a constant pressure sufiices for producing the pre-pressure.

A pump constructed in particular as a gear pump preferably serves as the source of this substantially constant pre-pressure and is driven by the driving shaft of the mechanism.

Further improvements and preferred constructional features of the invention are explained below in conjunction with the accompanying drawing, in which one embodiment of the invention is illustrated.

In the drawings:

FIG. 1 shows a longitudinal section through a driving mechanism constructed in accordance with the invention taken along the line l-I of FIG. 2;

FIG. 2 shows a transverse section through the mechanism on the line II-Il of FIG. 1;

FIG. 3 shows a transverse section on the line lIl-JH of FIG. 1;

FIG. 4 shows a partial transverse section on the line IV-IV of FIG. 1;

PEG. 5 shows a partial transverse section on the line VV of FIG. l;

FIG. 6 shows a partial section on the line VIVI of FIG. 1,

FIG. 7 is a sectional detail View of the cylinder housings coupling and FIG. 8 is a sectional detail view of the control rollers and grooves taken along VIII-VIII of FIG. 1.

A control plug 2 is fitted non-rotatably in a housing 1.

A bushing 4 formed with a series of radial ports is pressed into a drilling in a cylinder housing 3 and is secured against rotation by means of a grub screw 5. This cylinder housing is arranged to be rotatable with the drilling in its bushing 4 on the part 6 of the control plug 2 shown to the left in FIG. 1. The end of the shaft of an electric motor (not shown) serving as a driving machine is shown at 8'. This shaft drives a stub shaft 38 by Way of a non-slip flexible coupling 7, the stud shaft 38 being rotatably mounted in a three-part gear pump housing 68, 7 0, 72 and driving the cylinder housing 3 by way of a non-slip flexible coupling 75. The three-part housing 68, 70, 72 is rigidly connected with the housing 1 by means of threaded bolts 76 and securing keys 77. A gear wheel 79 is rotatably mounted in it on a spindle 78 and forms one part of a gear wheel pump, its teeth meshing with those of a gear wheel which is secured to the stub shaft 38. The gear pump formed by the two gear Wheels 79 and 80 draws oil from a reservoir via a duct 81 and a connection 82;, whereas the pressure duct is provided with the reference 83 and the pressure connection with the reference 84. The pump serves to supply a constant pressure, such as 15 atmospheres, for example.

Two setting or volume regulating rings 10, 11 are pivotally arranged in the housing 1 upon a spindle 9. The construction of the two regulating rings, of which the regulating ring 11 is shown in FIG. 2, is the same for each. The eccentric position of their bores 12 with respect to the axis 13 of the cylinder housing 3 and the control plug 2 is displaced by Whereas the axis 14 of the bore in the regulating ring 11 lies a certain distance below that of the axis 13 (in FIG. 2), the axis 52 of the bore in the regulating ring 10 (see FIG. 3) lies above the axis 13 by the same distance.

A running ring 19 is rotatably mounted in the two regulating rings 10, 11 by means of two roller bearings 15, 16 and two flange rings 17, 18 and its inner surfaces 20, 21 are inclined away from each other in a conical fashion. A series of pistons '22, 23 co-operates with each of these running surfaces 20, 21 and their rounded heads 24 lie against the corresponding running surfaces 20, 21. The relative movement between the piston head and the inner ring is thus converted into a pendulum movement of the piston 22 and 24. Moreover, the pistons are inserted obliquely in the cylinder body whereby the rolling path of the piston heads is widened. In the embodiment shown, 11 pistons 22 or 2.3 constitute each series of pistons and the two series together form a piston group. A piston group being mounted in a single cylinder housing.

The pistons which are arranged in the cylinder body of the regulating ring '10 have references 25, 26. The construction and arrangement correspond with that of the pistons 22, 23.

The pistons 25, 26 are arranged in the cylinder housing 3 and are rotated about the axis of shaft 38 by the cylinder housing 3 which is driven by the electric motor (not shown). The pistons 22, 23 are arranged in a cylinder housing 27 which is connected with the cylinder housing 3 by means of a non-slip coupling 28. The coupling 28 is of a type which prevents relative rotation between the cylinder housings 3 and 27, but permits the cylinder housings to be relatively radially displaceable in the direction of displacement caused by the fluid force within the pressure section of the control plug 2. Coupling 28 may consist of a diametrical groove 90 formed in the end of housing 27 which reseives a diametrically extending tongue 92 defined in the adjacent end of housing 3. The tilting pressure described is avoided by these members of the cylinder body. A multi-ported bushing 51 is likewise pressed into the cylinder housing 27. The two cylinder housings 3, 27 are driven in the direction of the arrow 39. A suction space 36' and a pressure space 31 are provided on the parts 6 of the control plug 2 in the region of the pistons 22, 23. In the corresponding way, the part 6 of the control plug includes a pressure space 49 and a suction space 50 in the region of the pistons 25, 26. The spaces 49, 50 are displaced by 180 with respect to the spaces 30, 31.

The control plug also includes four drillings 32, 33, 34, 35. The longitudinal drillings 32 and 35 form pressure channels. As shown in FIG. 4, the control plug 2 is provided with two notches 53, 54 by which the drillings 32 and 35 are connected with an annular space 55 provided in the housing 1. The drilling 56 establishes a connection between the annular space 25 and a pressure connection 57.

The longitudinal drillings 33, 34 form suction channels. For this purpose, the control plug 2 is provided with two notches 58, 59 as shown in FIG. by which the drillings 33 and 34 are connected with an annular space 60 provided in the housing 1. A drilling 61 establishes a connection with a suction pipe 62.

For further clarification, the suction channels are indicated with S and the pressure channels with D.

It is also possible to construct the two suction channels 33 and 34 and the two pressurechannels 32 and 35 separately from the control plug and so provide two completely separate pumps in the one unistructional unit.

Two diametrically-opposed longitudinal drillings 36, 39 are provided in the control plug 2 which communicate with an annular channel 64 provided on the plug 2 by way of two radial drillings 63, the annular channel 64 being connected via a drilling 65 with a connection 66. In a manner not shown, this connection 66 is coupled with a pressure connection 84 of the gear pumps 79, 80.

The longitudinal drilling 36 is provided in the region of the pistons 22, 23, and hence at the place where the suction space 30 passes into the pressure space 31, with a radial drilling 67 which merges into an axial groove 37 extending to the running surface of the plug 2. In a corresponding manner, the longitudinal drilling 39 is provided in the region of the pistons 25, 26, and hence at the place where the suction space 50 passes into the pressure space 49, with a radial drilling 69 which merges into an axial groove 71 provided on the running surface of the plug 2.

Radial drillings 73 are provided in the longitudinal drillings 36 and 39 but outside the region (the region) of the pistons 22, 23 and 25, 26, which connect with longitudinal grooves 74. These longitudinal grooves 74 only serve for lubrication, whereas the longitudinal grooves 37 and '71 serve to increase the silent running and vibration characteristics of the pump. By means of these grooves 37 and 71, each cylinder is subjected to pressure before completion of the suction stroke from an independent pressure source (in the embodiment shown, by the pressure delivered from the gear pump 79, 36), so that a return pulse of the pressure from the pressure chambers 31 and 49 into the cylinder spaces communicating with the suction chambers 30 and 50, due to the incomplete filling and the compressability of the oil by entrained air, cannot occur, whereby the oil column is maintained.

Regulation of the amount supplied by the pump is effected by pivoting the two regulating rings 10, 11 about the spindle 9 by means of the rollers 40 which engage in grooves 41 on control rollers 42 and 43. The two rollers 42 and 43 are connected together by gearing and are driven together by means of a pinion 44 aflixed to one of the roller shafts. In this way, it is ensured that the two regulating rings are always adjusted by the same amount with respect to each other.

The concept of subjecting the operating spaces to a pre-pressure at the end of the suction stroke shortly before beginning the pressure stroke can also be employed for steplessly variable hydrostatic driving mechanisms of other kinds.

Whereas the mechanism of the embodiment can be driven up to a pressure of about 150 to 300 atmospheres, the pressure of the gear pump which supplies the drillings 36 and 39 is approximately equal to 15 atmospheres.

In FIG. 1, assuming the cylinder housings 3 and 27 not being radially displaceable, but rather rigidly connected together forming an integral unit, the triangles 45, 46, 47, 48 indicate the pressure distribution which occurs on the edges of the pressure channels 31 and 49. It can thus be seen that the pressures in the triangles 46 and 47, acting at the geometrical centres of the triangles, form a tilting moment on the cylinder housings and control plug 2. A second tilting moment is represented by the triangles '45 and 48. The two moments are additive and would cause a marked tilting of the cylinder housings if the cylinder housings were not relatively radially displaceable in the direction of the forces exerted in channels 31 and 49, thus no bending or tilting moment is exerted on the cylinder housings but rather a purely radial force.

In the embodiment, it is assumed that the pre-pressure is supplied by a gear pump 79, which is driven from the machine which also drives the hydrostatic mechanism. It is also possible however to derive this pro-pressure from a quite independent pressure source, for example an independently driven pump. Instead of this, it is also possible to provide a pressure accumulator which supplies the pre-pressure independently of operation of the hydrostatic mechanism. In the two latter possibilities, the pre-pressure is also maintained during stoppage of the machine.

In the embodiment shown, four drillings 32, 33, 34, 35 are provided in the control plug. Such construction would permit two separate pump systems if dual intake, outlet and annular chambers are provided. Or only two longitudinal passages in control plug are necessary if it is desired to use common suction and pressure conduits for the various cylinder and piston groups.

assasas What I claim is:

1. In a hydraulic power transmission device, a housing, a valve pintle extending into said housing formed with longitudinal passages communicating with pressure and suction channels opening on the periphery of the pintle, at least one pair of annular cylinder housings axially spaced in contiguous relation on said pintle radially displaceable coupling means operatively interposed between said cylinder housings, pistons radially displaceahle in cylinders formed in each of said cylinder housings in two axially spaced annular rows, the cylinders of each housing selectively communicating with said channels, at least one pair of regulating rings, each ring carrying a ball bearing mounted race surrounding one of said cylinder housings, said pistons having rounded ends adapted to engage the inner periphery of said ball bearing race, a spindle supported in said housing spaced in parallel relation to the axis of said central pintle pivotally supporting said regulating rings, means equally adjusting the angular displacement of said regulating rings around said spindle in opposite directions, said suction and said pressure channels communicating with said cylinders of one cylinder housing being arranged diametrically opposed upon said pintle periphery to said suction and said pressure channels communicating with said cylinders of the other cylinder housing of said pair of cylinder housings.

2. In a hydraulic power transmission device as in claim 1, wherein the inner periphery of the race contacted by said pistons is formed by two conical surfaces converging inwardly and said two rows of pistons are relatively arranged slantingly diverging outwardly.

3. In hydraulic power transmission device as in claim 1 wherein said adjusting means for said regulating rings includes two rolls drivingly interconnected, said rolls being provided with helical grooves engaged by followers secured to said regulating rings diametrically opposite to said spindle.

4. A hydrostatic power transmission comprising in combination, a housing, a valve pintle extending into said housing formed with longitudinal passages communicating with pressure and suction channels opening on the periphery of the pintle, an even number of separate, adjacent annular cylinder housings rotatably supported on said pintle, radially reciprocable pistons mounted within cylinders defined in said cylinder housings, a regulating ring having an inner periphery engaged by said pistons cimcumscribing each of said cylindrical housings, means eccentrically adjusting said rings relative to the axis of said pintle whereby adjacent rings are eccentrically disposed to each other an equal degree from the pintle axis and radial displaceable coupling means interconnecting adjacent cylinder housings transmitting torque therebetween and permitting radial displacement between said cylinder housings in the direction of primary radial forces imposed on said cylindrical housings.

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